Method of making a honeycomb block collimator

ABSTRACT

A honeycomb block is made by winding a tungsten metal wire compactly around a core and then removing the core, thereby fabricating a compactly wound coil member. The coil members are arranged side by side and are bonded together with a metal paste bonding agent to form the honeycomb block.

United States Patent Abe et al. 1 June 20, 1972 [54] METHOD OF MAKING AHONEYCOMB 581 Field ofSearch ..29/4s5, 471.1, 472.3; 250/105, BLOCKCOLLIMATOR 250/71.5 R, 71.5 s

[72] Inventors: Isarnu Abe, Kawasaki; Hideo Yashiro, [56] ReferencesCited Tokyo; Naoyuki Sori, Tokyo; Sotaro Hatano, Tokyo; TomiyasuKatsumoto, UNITED STATES PATENTS T k T S ki, I k I s awa a1 3,407,30010/1968 Hansen ..250/105 3,543,384 12/1970 Hansen ..250/105 X [73]Assignee: Tokyo Shibaura Electric Co., Ltd.,

Kawasaki-shi, Japan Primary Examiner-Anthony L. Birch [22] Filed: Sept.18, 1970 Attorney-Flynn & Fr1shauf [21] Appl. No.: 73,573 [57] ABSTRACTRelated s A fi fi Data A honeycomb block is made by winding a tungstenmetal wire compactly around a core and then removing the core, therebycommuatlon'mpafl of 5611 1 p fabricating a compactly wound coil member.The coil mem- 1970 abandonedbers are arranged side by side and arebonded together with a 7 metal paste bonding agent to form the honeycombblock. [52] US. Cl ..29/47l.l, 250/105 [51] Int. Cl. ..G2lf 5/02, HOlj35/16 10 Claims, 3 Drawing Figures P'A'TENIEDauuzo m2 v f lama 485. mMil/0, Mm var! 50 ran MIT/M9,

By TIMIYAWA'IIWWM Tam $02047, INVENTORS 'flyk. 4

1 METHOD OF MAKING A HONEYCOMB BLOCK COLLIMATOR I I This is acontinuation-in-part ofapplication Ser. No. 726,041, filed May 2, 1968,now abandoned.

This invention relates to honeycomb blocks, and more particularly to amethod of making a honeycomb block for X-ray use.

Where medical treatment is conducted by photographing the interior ofthe human body using X-rays, or radiating said interior using a C sourceit is common practice to apply to the human body the X-rays generated bythe source or dif fused radiations such as gamma rays emitted from theCo after being focused by a collimator. This collimator is in the formof a honeycomb block prepared by laminating a plurality of thin plateshaving a large number of apertures therein. Since these numerousapertures are arranged in registration with each other, the incomingradiations are allowed to pass through them in such a manner that theyare collimated only within a specified range on the outlet side.

For convenience in description, there will now'be described a prior artcollimator or honeycomb block used in photographing the human body bymeans of X-rays. The thin plates forming the honeycomb block were madeof materials capable of readily absorbing X-rays, namely, high densitymaterials. These materials generally consisted of lead, gold, platinum,molybdenum, tungsten and tungsten alloys. The fabrication of thehoneycomb block from the aforementioned thin plates required the stepsof drilling a large number of apertures in the plates and laminatingthese perforated plates. The perforation of the thin plates was adifficult operation because the drilling of a large number of aperturesthrough hard and yet brittle materials such as tungsten reduced the lifeof a drilling tool and required long hours of work. Conversely whereapertures were perforated at close intervals in thin plates made of softmaterials such as'lead and gold, the portions of the plate between theapertures were often subject to deformation. Consequently there was thedrawback that high precision could not be obtained for the apertures.Further for this reason, there were limits to the extent of reducing theaperture intervals of the honeycomb block, namely, the thickness of theportions of the plate intervening between the apertures in order toelevate the passage of X-rays.

SUMMARY OF THE INVENTION The present invention is intended to provide alarge number of apertures not by perforating a thin plate, but bycompactly coiling metal wire made of, for example, molybdenum ortungsten into a tubularform, and bonding these compactly wound coilmembers close to each other, thereby fabricating a honeycomb-likemulti-hole block. The aforementioned tubular compactly wound coil memberis fabricated by closely coiling wires around a core and thereafterwithdrawing the core from the coil. Thus, the adjacent wire turns areintimately attached to each other. It will be apparent that in thiscase, the shape of the aperture or inner hollow space of the compactlywound coil member may be not only circular, but also may take anydesired polygonal form, for example, a triangle, square, rectangle orhexagon according to the shape of the core used. The word tubular isused herein to denote any of these various shapes. Where the hollowspace assumes any of the latter forms, for example, a square orrectangle, the compactly would coil members will have increased contactareas when arranged together, thus enabling the honeycomb block composedof such members to have a greater assembled strength.

Also where the metal wire itself used in forming a compactly wound coilmember has a polygonal, for example, a rectangular cross section ratherthan a circular one, namely, a ribbon-like form, there will be obtainedlarger contact areas between the wire turns, thus improving themechanical strength of the compactly wound coil member.

To integrate a plurality of compactly wound coil members into ahoneycomb block by close attachment side by side, there is used a metalpaste bonding agent, such as copper paste, silver paste, copper alloypaste or silver alloy paste. Among copper alloy pastes, for example,there are Cu-Zn pastes, and among silver alloy pastes, there areAg-Zn-Cu pastes. A metal paste is prepared by mixing together the metalpowders and an organic solvent such as butyl acetate, vinyl acetate, andamyl acetate in the proportion of l-2:l by weight.

The apertures of a honeycomb block used as a radiation collimator arepreferably arranged in a linear direction. However, where theseapertures must have a nonlinear arrangement for use in otherapplications, the compactly wound coil members are purposely deformedand assembled by the use of a metal paste bonding agent into any desiredtype of honeycomb block so as to have a nonlinear aperture arrangement.

The honeycomb block prepared according to the present invention allowsthe apertures for passing radiations to have any desired cross sectionalshape. Furthermore, all of the apertures will have a uniform dimensionalprecision and the honeycomb block as a whole will have preciselypositioned apertures free from any distortion.

Referring to fabricating problems, the honeycomb block of the presentinvention eliminates the necessity of drilling apertures in a thinplate. Since the only requirement is to wind'wiring about a core,thereis the advantage that manufacturing process will become much easier evenif wiring consists of materials such as tungsten which normally presentdifliculties in machining. Moreover, the crosswise and lengthwiseintervals between the apertures can be reduced to about 40 to 60microns, thus substantially increasing the radiation collimatingcapacity of the honeycomb block of the present invention over the priorart apparatus.

There will now be described the present invention by reference to theappended drawing in which:

FIG. 1 is a perspective of a honeycomb block according to an embodimentof the present invention;

FIG. 2 is a perspective of an enlarged part of the honeycomb block'ofFIG. 1, showing details of the compactly coiledwire turns; and

FIG. 3 is a perspective of assembled compactly wound coil members whoseaperture or interior hollow space as well as the cross section of thecomponent wire is of a different shape from those of FIG. 2.

EXAMPLE 1 Referring to FIG. 2, numeral 1 represents a substantiallytubular compactly woundcoil member prepared by winding a tungsten wirehaving a circular cross section so as to form a circular aperture, theadjacent wire turns being arranged intimately close to each other. Thecompactly wound coil member is prepared by heating a tungsten wirehaving a circular cross section 0.2mm in diameter to about 800 C tosoften it and winding it about a molybdenum core (not shown) in a mannerto cause the adjacent wire turns to be wound intimately close to eachother. When the coil is wound to a length of 20 mm the core is withdrawnto obtain a compactly wound coil member having an aperture diameter of3.1 mm and an outer diameter of 3.5 mm.

Next there are piled in a rectangular form a large number of compactlywound coil members thus prepared in such a manner that the adjacentapertures are set apart approximately 3.5 mm from center to center,thereby to form as shown in FIG. 1 a honeycomb block mm on each side and20 mm in depth. In this case, as illustrated in FIG. 2, a metal pastebonding agent 3 is filled into the gaps between the respective compactlywound oil members 1. The bonding agents consists of a copper pastecomprising electrolytic copper powders and a butyl acetate solutionmixed, 1:1 by weight. The honeycomb block fonned from the coil membersthus assembled is heated to a temperature of l,l50 to 1,200 C in ahydrogen atmosphere for 30 minutes. The copper component included in thebonding agent is thermally melted to be carried into all the intersticesbetween the respective coil members 1 and upon cooling, firmly bondsthem together, thus integrally fabricating a honeycomb block 2.

EXAMPLE 2 The coil material consists of a molybdenum wire having a crosssection 1 mm X 0.2 mm as shown in FIG. 3. The wire is compactly wound atnonnal room temperatures about a molybdenum core having a cross section3.0 mm X 3.0 mm to a length of 20 mm. After completion of coiling, thecore is drawn out to obtain a compactly wound coil member 4 having anaperture 3.1 mm X 3.1 mm and an external size 3.5 mm X 3.5 mm.Thereafter, over the circumferential surface of the compactly wound coilmember thus formed is sprayed a solution of a bonding agent 5 comprisingelectrolytic copper powders and a vinyl acetate solution, mixed 1:1 byweight. After evaporation of the solvent, there are piled a large numberof compactly wound coil members 4 in a rectangular form. These coilmembers are heated to a temperature of 1,l50 to 1,200 C for 30 minutesand are bonded together by the molten copper. Upon cooling, there isobtained a honeycomb block of approximately the same overall shape asthat shown in FIG. 1.

EXAMPLE 3 Compactly wound coil members are formed from tungsten wire asdescribed in Example 1, and these coil members are then piled in arectangular form, also as described in Example 1. In this case, a metalpaste comprising silver powders and a butyl acetate solution, mixed 1:1by weight, is filled into the gaps between respective coil members. Theassembly is then heated to a temperature of l, ll ,150 C in a hydrogenatmosphere for 20 minutes. Thereafter, upon cooling, the silvercomponent in the metal paste firmly bonds the coils together, thusintegrally fabricating a honeycomb block. The use of the silver pastepermits the fabrication of the honeycomb block to be effected at a lowertemperature than in the case of a copper paste. Also, a shorter heatingperiod is required.

EXAMPLE 4 Compactly wound coil members are formed from tungsten wire asdescribed in Example 1, and these coil members are then piled in arectangular form, also as described in Example 1. In this case, a metalpaste comprising copper alloy powders of 65% Bu and 35% Zn (by weight)and a butyl acetate solution, the copper alloy powders and butyl acetatesolution being mixed l:l by weight, is filled into the gaps betweenrespective coil members. The assembly is then heated to a temperature of950-1,000 C in a hydrogen atmosphere for 20 minutes. Thereafter, uponcooling, the silver component in the metal paste firmly bonds the coilstogether, thus integrally fabricating a honeycomb block.

EXAMPLE 5 Compactly wound rectangularly shaped coil members are formedfrom molybdenum wire as described in Example 2, and these coil membersare then piled in a rectangular form, also as described in Example 2. Inthis case, a silver alloy paste comprising silver alloy powders of 45%Ag, 25% Zn and 30% Cu (by weight) and an amyl acetate solution, thesilver alloy powders and amyl acetate solution being mixed 1:1 byweight, is applied to the assembly, also as in Example 2. The assemblyis then heated to a temperature of 800-900 C in a hydrogen atmospherefor 20 minutes. Thereafter, upon cooling, the silver alloy components inthe metal paste firmly bonds the boils together, thus integrallyfabricating a honeycomb block.

Generally, there is a tendency for tungsten and molybdenum not to becomeintimately bonded to the other metal. However, it has been found that byusing a metal paste of copper or silver alloy, this tendency not to bondis more easily overcome and the bonding operation can be effected ateven lower temperatures.

While the invention has been described in connection with some preferredembodiments thereof, the invention is not limited thereto and includesany modifications and alterations which fall within the scope of theinvention as defined in the appended claims.

We claim:

1. A method of making a honeycomb block used for collimation ofelectro-magnetic radiations in the frequency range of X-rays andgamma-rays comprising the steps of:

fabricating a number of coil members, each being fabricated by:

winding around a core with a high density metal wire selected from thegroup consisting of tungsten and molybdenum; and

thereafter drawing out said core to form a compactly wound coil member;and

firmly bonding together a plurality of said coil members side by side tothereby fabricate a honeycomb block by:

assembling a plurality of coil members in a predetermined arrangement;

filling a metal paste as a bonding agent among said plurality of coilmembers, said metal paste comprising powders of metal selected from thegroup consisting of copper, silver, copper alloy and silver alloy; and

heating the resultant assembly of coil members at a temperature of from800l,200 C in a hydrogen atmosphere.

2. A method according to claim 1 wherein said metal wire is tungsten andfurther comprising the step of heating said tungsten wire toapproximately 800 C prior to the winding step.

3. A method according to claim 1 wherein said assembling step is carriedout prior to filling said metal paste among said plurality of coilmembers, and said heating step is thereafter carried out.

4. A method according to claim 3 wherein said metal wire is tungsten.

5. A method according to claim 1 wherein said metal paste is sprayed onsaid plurality of coil members prior to assembling same, and saidheating step is thereafter carried out.

6. A method according to claim 5 wherein said metal wire is molybdenum.

7. A method according to claim 1 wherein said metal wire has asubstantially circular cross section.

8. A method according to claim 1 wherein said metal wire has asubstantially rectangular cross section.

9. A method according to claim 1 wherein each coil member is wound tohave a polygonal aperture.

10. A method according to claim 1 wherein each coil member is wound tohave a round aperture.

+22%? UNITED STATES PATENT OFFICE v CERTIFICATE 0F CORRECTION Patent NO.3,670,395 Dated June 20-, 1972 I v fl Isamu ABE et al It is certifiedthat error appears inv the above-identified patent and that said LetterePatent are hereby corrected as shown below:

Page 1 In the heading add the following Priority data:

- [30] Foreign Application Priority Data May 9, l967'Japan.......;..28893/67--'-'.

Signed and sealed this 51th day ofv December 1972.-

(SEAL) Attest:

EDWARD M.FLETCHER,JR; ROBERT GOTTSCHALK Attesting. Offioer vCommissioner of Patents

1. A method of making a honeycomb block used for collimation of electro-magnetic radiations in the frequency range of X-rays and gamma-rays comprising the steps of: fabricating a number of coil members, each being fabricated by: winding around a core with a high density metal wire selected from the group consisting of tungsten and molybdenum; and thereafter drawing out said core to form a compactly wound coil member; and firmly bonding together a plurality of said coil members side by side to thereby fabricate a honeycomb block by: assembling a plurality of coil members in a predetermined arrangement; filling a metal paste as a bonding agent among said plurality of coil members, said metal paste comprising powders of metal selected from the group consisting of copper, silver, copper alloy and silver alloy; and heating the resultant assembly of coil members at a temperature of from 800*-1,200* C in a hydrogen atmosphere.
 2. A method according to claim 1 wherein said metal wire is tungsten and further comprising the step of heating said tungsten wire to approximately 800* C prior to the winding step.
 3. A method according to claim 1 wherein said assembling step is carried out prior to filling said metal paste among said plurality of coil members, and said heating step is thereafter carried out.
 4. A method according to claim 3 wherein said metal wire is tungsten.
 5. A method according to claim 1 wherein said metal paste is sprayed on said plurality of coil members prior to assembling same, and said heating step is thereafter carried out.
 6. A method according to claim 5 wherein said metal wire is molybdenum.
 7. A method according to claim 1 wherein said metal wire has a substantially circular cross section.
 8. A method according to claim 1 wherein said metal wire has a substantially rectangular cross section.
 9. A method according to claim 1 wherein each coil member is wound to have a polygonal aperture.
 10. A method according to claim 1 wherein each coil member is wound to have a round aperture. 